Increased hay fever latest side effect of climate change

That annual scourge of the hay fever sufferer, ragweed, is benefiting greatly from shifts in the climate in some parts of North America, according to a new study from scientists at the US Department of Agriculture (USDA). This invasive wind-pollinated plant is often touted as producing the most allergenic pollens in the US.

The pollen production peaks as ragweed blooms after midsummer, and continues through to late summer. Now the Agricultural Research Service (ARS) has produced a study into 15 years of pollen data, investigating anecdotal signs of an increase in the ragweed pollen season - and whether it could be linked to climatic changes.

With 10% to 20% of Americans suffering from hay fever, any changes in that season could be having a big impact on their lives. Typical symptoms of hay fever include irritated puffy eyes, a streaming nose, sneezing, and a sore throat.

For the most severe sufferers, chronic sinusitis and asthmatic attacks are deeply unpleasant allergic reactions. Many of those experiencing hay fever have long claimed that they have to endure these symptom for longer now - and this study appears to back them up.

Pollen data from 10 locations, along a north-south section of North America, were assessed for ragweed pollen counts for each year from 1995 to 2009. Additionally, the team, led by Lewis Ziska of the ARS, looked at the number of frost-free days, and the timing of first fall frosts for each site.

What they found was that the ragweed season had indeed extended - for the more northerly study sites particularly - by as much as a month when compared to 1995. Additionally, those same sites also showed an increase in the number of frost free days, and a pushing back of the first fall frost. The correlation between the longer pollen season, and the delays in frost onset, were assessed to be strong.

ARS Administrator Edward B. Knipling states, in relation to climate change effects, that ''Studies like this also show us that these ecological shifts don't stop at crop production. They can also have a significant impact on public health.''

The warming in surface temperatures at higher latitudes, as described in this study, are firmly ascribed to man-made climate change by the IPCC (Intergovernmental Panel on Climate Change). So it seems that global warming has another affliction to add to the package of woes it has already delivered to Americans.

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